Preparation method, application and application device of red mud-biochar

Abstract

The invention aims at providing a preparation method, application and application device of red mud-biochar, and relates to the technical field of industrial and agricultural solid waste resource utilization, corn straw serves as biomass and is mixed with red mud for co-pyrolysis to prepare modified biochar, the composite material can prevent metal oxide from agglomeration, and the utilization rate of the red mud-biochar is increased. The surface adsorption sites of the biochar are increased, the adsorption capacity of the biochar to pollutants is improved, the oxidation-reduction active sites of the biochar are increased, the catalytic degradation performance of the biochar to organic pollutants is enhanced, the bisphenol A removal rate of the biochar during catalytic degradation of bisphenol A reaches up to 80% or above, and the requirements of modern industrial and agricultural solid waste resource utilization can be better met; the red mud-biochar composite material is collected through a filter membrane of the constant-flow purification device, and the situation that the powdery red mud-biochar composite material suspends in a reaction solution after catalytic degradation, and subsequent collection, activation and repeated utilization of the powdery red mud-biochar composite material are not facilitated is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field related to resource utilization of industrial and agricultural solid wastes, and in particular to a method for preparing red mud-biochar and its application and application device. Background Art

[0002] Red mud, also known as red mud, is an alkaline industrial solid waste discharged after the extraction of alumina from bauxite. It generally has a high iron oxide content. For every ton of alumina produced, about 1 to 2 tons of harmful red mud are discharged. Red mud is called a hazardous waste due to its high alkalinity (pH 10-12.5). Large-scale disposal of red mud in industrial landfills poses a significant risk of pollution to the environment. As rainwater washes away, the alkali in the red mud will be dissolved, which may pollute surface water and groundwater.

[0003] Biochar (BC) is a new type of inexpensive carbonaceous material produced from cheap waste biomass. Due to its large specific surface area, excellent electrical conductivity and good stability, BC has been widely used as a carrier for the degradation of pollutants.

[0004] Bisphenols (BPs) are widely used in the production of polycarbonate and epoxy resins, and are found in items such as baby bottles, plastic water bottles, food storage containers, dental fillings, thermal and pressure-sensitive paper, banknotes, receipts, and toys. Bisphenol A (BPA) is the most representative compound among them, and there is almost no way to completely decompose it in nature. BPA can interfere with the human endocrine system at low doses, causing people to suffer from various diseases. BPA can enter the environment in a variety of ways, the most important of which is the direct discharge of wastewater into the environment from sewage treatment plants.

[0005] At present, the conventional treatment processes (such as biological treatment, chlorination, and ozonation) of sewage treatment plants do not have significant degradation capabilities for BPA, because these processes are mainly used to remove BOD, COD, nitrogen, and phosphorus. In wastewater treatment technology, advanced oxidation technology for free radical degradation of stubborn pollutants has attracted people's attention. The patent with publication number CN113908800B discloses a method for removing bisphenol A from sewage using modified red mud. The removal rate of bisphenol A using modified red mud is low and does not reach 70%, which cannot well meet the needs of industrial and agricultural solid waste resource utilization. In addition, in the process of removing bisphenol A, the prepared modified red mud is easily suspended in the sewage when added to the sewage, which makes it difficult to separate the catalyst material from the liquid. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention provides the following technical solutions:

[0007] A preparation method and application of red mud-biochar and an application device, wherein the preparation method comprises the following steps:

[0008] S1, washing and drying the straw, and sieving to obtain small biomass particles, and drying the red mud, and sieving to obtain small red mud particles;

[0009] S2, mixing biomass and red mud in proportion, adding ultrapure water, stirring magnetically, and drying to obtain a solid mixture of red mud and biomass;

[0010] S3, placing the mixture in a muffle furnace, heating it continuously for 2 h under a N2 atmosphere, and then naturally cooling it to room temperature to obtain a mixed material;

[0011] S4, removing free biochar and free red mud in the mixed material by density classification to obtain a red mud-biochar composite material;

[0012] S4.1, adding the obtained red mud-biochar mixed material and sodium iodide solution into a centrifuge tube, shaking well, standing, and centrifuging to remove the supernatant;

[0013] S4.2, adding sodium iodide solution and shaking to mix the remaining solid residue in the centrifuge tube, and destroying the agglomerated particles by ultrasonic treatment;

[0014] S4.3, after the ultrasonic treatment, the mixture is allowed to stand, and then centrifuged, vacuum filtered, and dried to obtain a red mud-biochar composite material.

[0015] Furthermore, the straw is corn straw, and the straw is washed with clean water for 3 to 5 times to remove impurities on its surface. The washed straw is dried and passed through a 60-mesh sieve to obtain small biomass particles; the red mud is dried and passed through a 100-mesh sieve to obtain small red mud particles.

[0016] Furthermore, the mixing ratio of the biomass and red mud includes 1:1, 2:1, 3:1, and 9:1. An appropriate amount of ultrapure water is added to the above ratios, mixed and magnetically stirred for 24 hours, and then dried to obtain a solid mixture of red mud and biomass.

[0017] Furthermore, the solid mixture was placed in a muffle furnace, and heated to 300° C., 450° C., and 600° C. at a heating rate of 5° C. / min under a N 2 atmosphere for 2 h, and naturally cooled to room temperature to obtain a mixed material.

[0018] Furthermore, the obtained red mud-biochar mixture was transferred to a 50 mL centrifuge tube and an appropriate amount of 1.8 g / cm 3 The ratio of the mass of the red mud-biochar mixture to the volume of the sodium iodide solution (M:V) in the centrifuge tube is 1:4. The centrifuge tube is manually shaken up and down slowly for 5 times to moisten the mixture, and then allowed to stand for 30 minutes and centrifuged at 3500 rpm for 30 minutes. The supernatant is a mixed solution with pure biochar and is discarded.

[0019] The solid residue remaining in the centrifuge tube was added with the same volume density of 1.8 g / cm 3 The sodium iodide solution was manually shaken up and down 25 times to disperse it. 3 Ultrasonic treatment was performed to destroy agglomerated particles; during the ultrasonic treatment, an ice water bath was used around the sample to ensure that the liquid temperature in the sample was <50°C;

[0020] After the ultrasound was finished, the mixture was allowed to stand for 30 minutes and centrifuged at 3500 rpm for 30 minutes. The supernatant was filtered using a vacuum filtration device, and the residue on the filter paper was the red mud-biochar composite material. The obtained red mud-biochar composite material was dried in an oven at 40°C until dry.

[0021] Furthermore, the red mud-biochar composite material and the constant flow purification device constitute a bisphenol A catalytic degradation system to degrade BPA:

[0022] The bisphenol A catalytic degradation system is composed of red mud-biochar obtained by the red mud-biochar preparation method and a constant flow purification device, wherein the constant flow purification device comprises a bracket, a reaction tank, a constant flow pump and a conduit, wherein the reaction tank is fixedly mounted on the bracket, a filter membrane is arranged in the reaction tank, a switchable sampling port is arranged below the reaction tank, the upper and lower ends of the reaction tank are respectively connected to the constant flow pump through the conduit, the conduit is connected to the inside of the reaction tank, and the liquid at the bottom of the reaction tank is transported to the top of the reaction tank through the constant flow pump, so that the liquid in the reaction tank circulates.

[0023] The catalytic degradation steps of bisphenol A are as follows:

[0024] In the first step, 60 mg of red mud-biochar composite material was evenly suspended in 100 ml of 15 mg / L BPA solution;

[0025] The second step is to pour the mixed suspension into a constant flow purification device, so that the mixed suspension circulates in the constant flow purification device and reaches adsorption equilibrium after 30 minutes of circulation;

[0026] In the third step, PMS is added to circulate the mixed suspension in the constant flow purification device, and the PMS concentration in the whole system reaches 6mM;

[0027] In the fourth step, 0.5 ml of the solution was taken from the sampling port of the reaction system at 0, 10, 20, 50, 80, 120, and 180 min, respectively, and immediately quenched with 0.5 ml of methanol, and then transferred to a liquid phase bottle, and the concentration of BPA was determined by high performance liquid chromatography.

[0028] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0029] 1. The present invention provides a method for preparing red mud-biochar, its application and application device, using corn stalks as biomass, and mixing them with red mud for co-pyrolysis to prepare modified biochar. The co-pyrolysis of corn stalks and red mud can reduce the pollution caused to the environment and improve energy efficiency. Due to the high iron oxide content of red mud, after being mixed with corn stalks for co-pyrolysis, a biochar-metal composite material is formed. The composite material can not only prevent the agglomeration of metal oxides, increase the adsorption sites on the surface of biochar, and improve the adsorption capacity of pollutants, but also increase the redox active sites of biochar, and enhance the catalytic degradation performance of organic pollutants, so that the removal rate of bisphenol A during the catalytic degradation of bisphenol A is as high as 80% or more, which has high practicality and can well meet the needs of modern industrial and agricultural solid waste resource utilization;

[0030] 2. The red mud-biochar composite material prepared by the preparation method of the present application and the constant flow purification device constitute a bisphenol A catalytic degradation system. Bisphenol A and the red mud-biochar composite material are placed in the constant flow purification device in proportion, circulated, and the red mud-biochar composite material is collected by the filter membrane of the constant flow purification device to avoid the powdered red mud-biochar composite material being suspended in the reaction solution after catalytic degradation, which is not conducive to its subsequent collection, activation and repeated utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the constant current purification device of the present invention;

[0032] Figure 2 Schematic diagram of the degradation of BPA by composite materials with different proportions at 300°C;

[0033] Figure 3 Schematic diagram of the degradation of BPA by composite materials with different proportions at 450°C;

[0034] Figure 4 Schematic diagram of the degradation of BPA by composite materials with different proportions at 600°C;

[0035] Figure 5 Schematic diagram of the degradation of BPA by RM600, YM600 and PMS.

[0036] In the figure: bracket-1, reaction tank-2, filter membrane-3, catheter-4, constant flow pump-5, sampling port-6, liquid addition port-7. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Embodiment 1:

[0039] See also Figure 1-5 , a preparation method and application of red mud-biochar and an application device, the preparation method comprising the following steps:

[0040] S1, crushing corn stalks and washing them with clean water for 3 to 5 times to remove impurities on the surface, drying the washed corn stalks, and passing them through a 60-mesh sieve to obtain small biomass particles; crushing red mud and drying it, and passing it through a 100-mesh sieve to obtain small red mud particles;

[0041] S2, mixing biomass, red mud, and an appropriate amount of ultrapure water (the mass ratio of biomass to red mud is 1:1, 2:1, 3:1, 9:1), stirring magnetically for 24 hours, and drying to obtain a solid mixture of red mud and biomass;

[0042] S3, placing the mixture in a muffle furnace, heating it continuously for 2 h under a N2 atmosphere, and then naturally cooling it to room temperature to obtain a mixed material;

[0043] The mixture was placed in a muffle furnace and heated to 300°C, 450°C, and 600°C at a heating rate of 5°C / min under N2 atmosphere for 2 h, and then naturally cooled to room temperature to obtain mixed materials, which were named as follows:

[0044] BC300@1:1, BC300@2:1, BC300@3:1, BC300@9:1;

[0045] BC450@1:1, BC450@2:1, BC450@3:1, BC450@9:1;

[0046] BC600@1:1, BC600@2:1, BC600@3:1, BC600@9:1;

[0047] S4, removing free biochar and free red mud in the mixed material by density classification to obtain a red mud-biochar composite material;

[0048] S4.1, transfer the obtained red mud-biochar mixture into a 50 mL centrifuge tube and add an appropriate amount of 1.8 g / cm 3The ratio (M:V) of the mass (g) of the red mud-biochar mixture to the volume (mL) of the sodium iodide solution in the centrifuge tube was 1:4. The centrifuge tube was manually shaken up and down 5 times to moisten the mixture. After standing for 30 minutes, it was centrifuged at 3500 rpm for 30 minutes. At this time, the supernatant was a mixed solution with pure biochar and was discarded.

[0049] S4.2, the solid residue remaining in the centrifuge tube is added with the same volume density of 1.8g / cm 3 The sodium iodide solution was manually shaken up and down 25 times to disperse it. 3 Ultrasonic treatment was performed to destroy agglomerated particles; during the ultrasonic treatment, an ice water bath was used around the sample to ensure that the liquid temperature in the sample was <50°C;

[0050] S4.3, after the ultrasonic treatment is completed, the mixture is allowed to stand for 30 minutes and then centrifuged at 3500 rpm for 30 minutes. The supernatant is filtered using an existing vacuum filtration device. The residue on the filter paper is the red mud-biochar composite material, which is then dried in an oven at 40°C to obtain a dry red mud-biochar composite material.

[0051] Embodiment 2:

[0052] According to Example 1, the red mud-biochar preparation method is used to prepare a red mud-biochar composite material and a constant flow purification device to form a bisphenol A catalytic degradation system to degrade BPA:

[0053] The bisphenol A catalytic degradation system is composed of red mud-biochar obtained by the red mud-biochar preparation method and a constant flow purification device. The constant flow purification device is as follows: Figure 1 As shown, it includes a bracket 1, a reaction tank 2, a constant flow pump 5 and a conduit 4, wherein the reaction tank 2 is fixedly mounted on the bracket 1, a filter membrane 3 is arranged in the reaction tank, a switchable sampling port 6 is arranged below the reaction tank 2, the upper and lower ends of the reaction tank 2 are respectively connected to the constant flow pump 5 through the conduit 4, the conduit 4 is connected to the inside of the reaction tank 2, and the liquid at the bottom of the reaction tank is transported to the top of the reaction tank 2 through the constant flow pump 5, so that the liquid in the reaction tank circulates;

[0054] In this embodiment, the pore size of the filter membrane 3 is 0.22 μm, and a liquid inlet 7 is provided at the top of the reaction tank 2. The purpose of designing the constant flow purification device in this application is that since the prepared red mud-biochar complex is a powdered material, directly adding it to the aqueous solution as a catalyst to degrade BPA will cause the red mud-biochar complex to be suspended in the reaction liquid, which makes it difficult to separate the catalyst material from the liquid, and is not conducive to its subsequent collection, activation, and repeated use. In order to overcome this difficulty, the present invention forms a catalytic degradation system with the red mud-biochar complex material and the constant flow purification device;

[0055] The catalytic degradation steps of bisphenol A are as follows:

[0056] In the first step, 60 mg of red mud-biochar composite material was evenly suspended in 100 ml of 15 mg / L BPA solution;

[0057] In the second step, the mixed suspension is poured into the reaction tank 2 of the constant flow purification device from the liquid adding port 7, and the constant flow pump 5 is started to circulate the mixed suspension in the constant flow purification device, and the adsorption equilibrium is reached after the circulation for 30 minutes;

[0058] The third step is to turn off the constant flow pump 5, add PMS, and then turn on the constant flow pump 5 to make the PMS concentration of the mixed suspension reach 6mM and circulate in the reaction tank 2;

[0059] In the fourth step, 0.5 ml of the solution was taken from the sampling port of the reaction system at 0, 10, 20, 50, 80, 120, and 180 min, respectively, and immediately quenched with 0.5 ml of methanol, and then transferred to a liquid phase bottle, and the concentration of BPA was determined by high performance liquid chromatography. The concentration of BPA was determined by high performance liquid chromatography (HPLC), and its mobile phase was 50% deionized water and 50% acetonitrile solution, the flow rate was 1 mL / min, and the wavelength of the ultraviolet detector was 280 nm.

[0060] Embodiment 3:

[0061] According to Example 1-2, at 300°C, the degradation efficiency of BPA by the red mud-biochar composite material prepared by mixing corn stalks (biomass) with red mud at different ratios is as follows: Figure 2 As shown:

[0062] The degradation rate of BC300@1:1 reached 9% within three hours;

[0063] The degradation rate of BC300@2:1 reached 49% within three hours;

[0064] The degradation rate of BC300@3:1 reached 61% within three hours;

[0065] The degradation rate of BC300@9:1 reached 51% within three hours;

[0066] After comparison, it was found that the composite material formed by co-pyrolysis of corn straw and red mud at a mass ratio of 3:1 at 300°C had the best degradation effect.

[0067] At 450℃, the degradation efficiency of BPA by red mud-biochar composite materials prepared at different ratios of corn straw (biomass) and red mud is as follows: Figure 3 As shown:

[0068] The degradation rate of BC450@1:1 reached 25% within three hours;

[0069] The degradation rate of BC450@2:1 reached 34% within three hours;

[0070] The degradation rate of BC450@3:1 reached 39% within three hours;

[0071] The degradation rate of BC450@9:1 reached 22% within three hours;

[0072] After comparison, it was found that the composite material formed by co-pyrolysis of corn stalks and red mud at a mass ratio of 3:1 at 450°C had the best degradation effect.

[0073] At 600℃, the degradation efficiency of BPA by red mud-biochar composite materials prepared by corn straw (biomass) and red mud at different ratios is as follows: Figure 4 As shown:

[0074] The degradation rate of BC600@1:1 reached 49% within three hours;

[0075] The degradation rate of BC600@2:1 reached 52% within three hours;

[0076] The degradation rate of BC600@3:1 reached 79% within three hours;

[0077] The degradation rate of BC600@9:1 reached 90% within three hours;

[0078] After comparison, it was found that at 600°C, the composite material formed by co-pyrolysis of corn stalks and red mud in a mass ratio of 9:1 had the best degradation effect, reaching 90%, which is much higher than the removal rate of the prior art CN113908800B (less than 70%), and can better meet the needs of industrial and agricultural solid waste resource utilization;

[0079] Moreover, the adsorption capacity of all composite materials prepared at 600°C is stronger than that of the composite materials prepared at 300°C and 400°C.

[0080] Embodiment 4:

[0081] According to Examples 1-3, this example verifies the necessity of co-pyrolysis of corn stalks and red mud at 600°C. The degradation effects of YM600 prepared by pyrolysis of corn stalks alone and RM600 prepared by pyrolysis of red mud alone at 600°C and PMS alone are shown in Figure 1. Figure 5 As shown:

[0082] RM600 achieved a 12% degradation rate of BPA within three hours;

[0083] YM600 achieved a 43% degradation rate of BPA within three hours;

[0084] PMS achieved 18% degradation of BPA within three hours;

[0085] By comparison, it can be proved that at 600°C, the degradation effect of the composite material formed by co-pyrolysis of corn straw and red mud is greater than that of single red mud pyrolysis and single corn straw pyrolysis, which proves the necessity of co-pyrolysis.

[0086] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing red mud-biochar, characterized in that: The following steps are involved: S1, washing and drying the straw, and sieving to obtain small biomass particles, and drying the red mud, and sieving to obtain small red mud particles; S2, mixing biomass and red mud in proportion, adding ultrapure water, stirring magnetically, and drying to obtain a solid mixture of red mud and biomass; S3, placing the mixture in a muffle furnace, heating it continuously for 2 h under a N2 atmosphere, and then naturally cooling it to room temperature to obtain a mixed material; S4, removing free biochar and free red mud in the mixed material by density classification to obtain a red mud-biochar composite material; S4.1, adding the obtained red mud-biochar mixed material and sodium iodide solution into a centrifuge tube, shaking well, standing, and centrifuging to remove the supernatant; S4.2, adding sodium iodide solution and shaking to mix the remaining solid residue in the centrifuge tube, and destroying the agglomerated particles by ultrasonic treatment; S4.3, after the ultrasonic treatment, the mixture is allowed to stand, and then centrifuged, vacuum filtered, and dried to obtain a red mud-biochar composite material.

2. The method for preparing red mud-biochar according to claim 1, characterized in that: In S1, the straw is corn straw, and the corn straw is washed with clean water for 3 to 5 times to remove impurities on the surface. The washed straw is dried and passed through a 60-mesh sieve to obtain small biomass particles; the red mud is dried and passed through a 100-mesh sieve to obtain small red mud particles.

3. The method for preparing red mud-biochar according to claim 1, characterized in that: In S2, the mixing ratio of biomass and red mud includes 1:1, 2:1, 3:1, and 9:

1. Ultrapure water is added and mixed with magnetic stirring for 24 hours, and then dried to obtain a solid mixture of red mud and biomass.

4. The method for preparing red mud-biochar according to claim 1, characterized in that: In S3, the temperature is raised to 300-600° C. at a heating rate of 5° C. / min under a N 2 atmosphere and maintained for 2 h, and then naturally cooled to room temperature to obtain a mixed material.

5. The method for preparing red mud-biochar according to claim 1, characterized in that: In S4.1 and S4.2, the volume density of the sodium iodide solution is 1.8 g / cm 3 ; In S4.1, the obtained red mud-biochar mixed material is transferred to a 50 mL centrifuge tube, and 28 mL of an appropriate amount of sodium iodide solution is added. The ratio of the mass of the red mud-biochar mixed material to the volume of the sodium iodide solution in the centrifuge tube is 1:

4. The centrifuge tube is manually shaken up and down slowly for 5 times to moisten the mixture, and then allowed to stand for 30 minutes, centrifuged at 3500 rpm for 30 minutes, and the supernatant in the centrifuge tube is removed; In S4.2, the solid residue in the centrifuge tube was added with 28 mL of sodium iodide solution, and the tube was manually shaken up and down 25 times to disperse it. 3 Ultrasonic treatment was performed to destroy agglomerated particles. During the ultrasonic treatment, an ice water bath was used around the sample to ensure that the liquid temperature in the sample was <50°C. In S4.3, after the ultrasonic treatment, the mixture was allowed to stand for 30 minutes, centrifuged at 3500 rpm for 30 minutes, and filtered through a vacuum filtration device. The residue on the filter paper was the red mud-biochar composite material. The red mud-biochar composite material was then placed in an oven at 40° C. and dried.

6. Use of the red mud-biochar prepared by the method according to any one of claims 1 to 5 in the degradation of bisphenol A.

7. A bisphenol A catalytic degradation system, characterized in that: The red mud-biochar prepared by the method described in any one of claims 1 to 5 is composed of a constant flow purification device.

8. The system according to claim 7, characterized in that The constant flow purification device comprises a bracket, a reaction tank, a constant flow pump and a conduit. The reaction tank is fixedly mounted on the bracket, a filter membrane is arranged in the reaction tank, a sampling port is arranged below the reaction tank, the upper and lower ends of the reaction tank are respectively connected to the constant flow pump through the conduit, the conduit is connected to the inside of the reaction tank, and the liquid in the reaction tank is circulated through the constant flow pump.

9. Use of the system according to claim 7 or 8 in the degradation of bisphenol A, characterized in that: The following steps are involved: In the first step, 60 mg of red mud-biochar composite material was evenly suspended in 100 ml of 15 mg / L BPA solution; The second step is to pour the mixed suspension into a constant flow purification device, so that the mixed suspension circulates in the constant flow purification device and reaches adsorption equilibrium after 30 minutes of circulation; In the third step, PMS is added to circulate the mixed suspension in the constant flow purification device, and the PMS concentration in the whole system reaches 6mM; In the fourth step, 0.5 ml of the solution was taken from the sampling port of the reaction system at 0, 10, 20, 50, 80, 120, and 180 min, respectively, and immediately quenched with 0.5 ml of methanol, and then transferred to a liquid phase bottle, and the concentration of BPA was determined by high performance liquid chromatography.

Images